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Abstract:

A method of evaluating the performance of a magnetic recording system,
comprising measuring a first set of finite impulse response filter tap
values at time t1, measuring a second set of finite impulse response
filter tap values are measured at time t2, where time t2 is subsequent to
time t1, and calculating an actual loss parameter using the first set of
tap values and the second set of tap values. The method then compares the
actual loss parameter with a total effective loss threshold.

Claims:

1. A method of evaluating the performance of a data storage device,
comprising:establishing a total effective loss parameter
threshold;determining an actual total effective loss parameter for said
data storage device;operative if said actual total effective loss
parameter is greater than said total effective loss parameter threshold,
taking said data storage device out of service.

2. The method of claim 1, further comprising:operative if said actual
total effective loss parameter is not greater than said total effective
loss parameter threshold, using said actual total effective loss
parameter determining a future time when a total effective loss parameter
for said data storage device will be greater than said total effective
loss parameter threshold; andscheduling said data storage device for
evaluation at said future time.

3. The method of claim 1, wherein said determining an actual total
effective loss parameter comprises:measuring a first plurality of finite
impulse response ("FIR") taps at time t1; anddetermining a first FIR
transfer function by computing a Fourier Transform of the first plurality
of FIR taps.

4. The method of claim 3, further comprising:measuring a second plurality
of FIR taps at time t2; anddetermining a second FIR transfer function by
computing a Fourier Transform of the second plurality of FIR taps;wherein
time t2 is subsequent to time t1.

5. The method of claim 4, further comprising determining a FIR magnitude
response ratio between time t2 and time t1 using said first FIR transfer
function and said second FIR transfer function.

6. The method of claim 5, further comprising calculating said actual
effective loss parameter using a Wallace spacing loss function and said
FIR magnitude response ratio between time t2 and time t1.

8. An article of manufacture comprising a computer readable medium
comprising computer readable program code disposed therein for evaluating
the performance of a magnetic recording system, the computer readable
program code comprising a series of computer readable program steps to
effect:retrieving a pre-determined total effective loss parameter
threshold;determining an actual total effective loss parameter for said
data storage device;operative if said actual total effective loss
parameter is greater than said total effective loss parameter threshold,
generating a message to take said data storage device out of service.

9. The article of manufacture of claim 1, the computer readable program
code comprising a series of computer readable program steps to
effect:operative if said actual total effective loss parameter is not
greater than said total effective loss parameter threshold, using said
actual total effective loss parameter determining a future time when a
total effective loss parameter for said data storage device will be
greater than said total effective loss parameter threshold; andscheduling
said data storage device for evaluation at said future time.

10. The article of manufacture of claim 1, wherein said computer readable
program code to determining an actual total effective loss parameter
further comprises a series of computer readable program steps to
effect:measuring a first plurality of finite impulse response ("FIR")
taps at time t1; anddetermining a first FIR transfer function by
computing a Fourier Transform of the first plurality of FIR taps.

11. The article of manufacture of claim 10, the computer readable program
code further comprising a series of computer readable program steps to
effect:measuring a second plurality of FIR taps at time t2;
anddetermining a second FIR transfer function by computing a Fourier
Transform of the second plurality of FIR taps;wherein time t2 is
subsequent to time t1.

12. The article of manufacture of claim 11, the computer readable program
code further comprising a series of computer readable program steps to
effect determining a FIR magnitude response ratio between time t2 and
time t1 using said first FIR transfer function and said second FIR
transfer function.

13. The article of manufacture of claim 12, the computer readable program
code further comprising a series of computer readable program steps to
effect calculating said actual effective loss parameter using a Wallace
spacing loss function and said FIR magnitude response ratio between time
t2 and time t1.

15. A computer program product encoded in a computer readable medium and
usable with a programmable computer processor for evaluating the
performance of a magnetic recording system, the computer program product
comprising:computer readable program code which causes said programmable
processor to measure a first total effective loss parameter at a time
t1;computer readable program code which causes said programmable
processor to retrieve a pre-determined total effective loss parameter
threshold;computer readable program code which, if said actual total
effective loss parameter is greater than said total effective loss
parameter threshold, causes said programmable processor to take said data
storage device out of service.

16. The computer program product of claim 1, further comprising:computer
readable program code which, if said actual total effective loss
parameter is not greater than said total effective loss parameter
threshold, causes said programmable processor to use said actual total
effective loss parameter to determine a future time when a total
effective loss parameter for said data storage device will be greater
than said total effective loss parameter threshold and schedule said data
storage device for evaluation at said future time.

17. The computer program product of claim 15, wherein said computer
readable program code to determine an actual total effective loss
parameter further comprises:computer readable program code which causes
said programmable processor to measure a first plurality of finite
impulse response ("FIR") taps at time t1computer readable program code
which causes said programmable processor to determine a first FIR
transfer function by computing a Fourier Transform of the first plurality
of FIR taps.

18. The computer program product of claim 17, wherein said computer
readable program code to determine an actual total effective loss
parameter further comprises:computer readable program code which causes
said programmable processor to measure a second plurality of FIR taps at
time t2; andcomputer readable program code which causes said programmable
processor to determine a second FIR transfer function by computing a
Fourier Transform of the second plurality of FIR taps

19. The computer program product of claim 18, further comprising computer
readable program code which causes said programmable processor to
determine a FIR magnitude response ratio between time t2 and time t1
using the first FIR transfer function and the second FIR transfer
function.

20. The computer program product of claim 19, further comprising computer
readable program code which causes said programmable processor to
calculating said actual effective loss parameter using a Wallace spacing
loss function and said FIR magnitude response ratio between time t2 and
time t1.

Description:

FIELD OF THE INVENTION

[0001]Various implementations, and combinations thereof, are related to
evaluation of a data storage device by determining magnetic spacing
losses.

BACKGROUND OF THE INVENTION

[0002]Data storage subsystems include various components for causing a
read/write head to write to and read from a data storage medium. A
recording channel is the path between a data format control and the data
storage medium. Within the recording channel, a write signal is delivered
to a transducer of a read/write head for recording data on the data
storage medium, and a read signal is generated by a read transducer
disposed on the read/write head.

[0003]Among many potential failure mechanisms of storage devices is
degradation of the playback signal quality or magnitude. Degradation of
playback signal may arise from any of several conditions, such as an
increase in the head to storage medium spacing, an increase in the
thickness of the air film between the head and storage medium, formation
of stationary media debris particulates on the head air bearing surface,
pole tip recession occurring over time in a magnetic gap of write or read
head transducers, and the like.

SUMMARY OF THE INVENTION

[0004]In one embodiment, a method of evaluating the performance of a data
storage device is presented. The results of such an evaluation may be
used for failure prediction, storage device design, storage device
optimization.

[0005]The method establishes a total effective loss parameter threshold,
determines an actual total effective loss parameter for the data storage
device, and if the actual total effective loss parameter is greater than
the total effective loss parameter threshold, the method takes the data
storage device out of service.

[0006]In another embodiment, an article of manufacture including a
computer readable medium including computer readable program code
disposed therein to evaluate the performance of a data storage device.
The computer readable program code includes a series of computer readable
program steps to effect retrieving a pre-determined total effective loss
parameter threshold, determining an actual total effective loss parameter
for said data storage device, and if said actual total effective loss
parameter is greater than said total effective loss parameter threshold,
generating a message to take the data storage device out of service.

[0007]In yet another embodiment, a computer program product encoded in a
computer readable medium and usable with a programmable computer
processor for evaluating the performance of a magnetic recording system
is present. The computer program product includes computer readable
program code which causes the programmable processor to retrieve a
pre-determined total effective loss parameter threshold, determine an
actual total effective loss parameter for said data storage device, and
if said actual total effective loss parameter is greater than said total
effective loss parameter threshold, taking the data storage device out of
service.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008]The invention will be better understood from a reading of the
following detailed description taken in conjunction with the drawings in
which like reference designators are used to designate like elements, and
in which:

[0009]FIG. 1 is an illustration of an exemplary hardware and software
environment in which embodiments of the present invention are
implemented;

[0010]FIG. 2 is an illustration of an exemplary tape drive unit of FIG. 1;

[0017]This invention is described in preferred embodiments in the
following description with reference to the Figures, in which like
numbers represent the same or similar elements. Reference throughout this
specification to "one embodiment," "an embodiment," or similar language
means that a particular feature, structure, or characteristic described
in connection with the embodiment is included in at least one embodiment
of the present invention. Thus, appearances of the phrases "in one
embodiment," "in an embodiment," and similar language throughout this
specification may, but do not necessarily, all refer to the same
embodiment.

[0018]The described features, structures, or characteristics of the
invention may be combined in any suitable manner in one or more
embodiments. In the following description, numerous specific details are
recited to provide a thorough understanding of embodiments of the
invention. One skilled in the relevant art will recognize, however, that
the invention may be practiced without one or more of the specific
details, or with other methods, components, materials, and so forth. In
other instances, well-known structures, materials, or operations are not
shown or described in detail to avoid obscuring aspects of the invention.

[0019]The schematic flow chart included are generally set forth as logical
flow chart diagrams. As such, the depicted order and labeled steps are
indicative of one embodiment of the presented method. Other steps and
methods may be conceived that are equivalent in function, logic, or
effect to one or more steps, or portions thereof, of the illustrated
method. Additionally, the format and symbols employed are provided to
explain the logical steps of the method and are understood not to limit
the scope of the method. Although various arrow types and line types may
be employed in the flow chart diagrams, they are understood not to limit
the scope of the corresponding method. Indeed, some arrows or other
connectors may be used to indicate only the logical flow of the method.
For instance, an arrow may indicate a waiting or monitoring period of
unspecified duration between enumerated steps of the depicted method.
Additionally, the order in which a particular method occurs may or may
not strictly adhere to the order of the corresponding steps shown.

[0020]Applicants' invention is described herein in a data storage
embodiment utilizing a plurality of tape drives and a plurality of
magnetic tape storage media. This description should not be taken as
limiting. Rather, Applicants' invention may be used to evaluate the
performance of storage devices generally.

[0021]Referring now to FIG. 1, illustrates a hardware and software
environment in which one embodiment of the present invention is
implemented. Host computer 102 includes, among other programs, a storage
management program 104. In certain embodiments, host computer 102
comprises a single computer. In alternative embodiments, host computer
102 comprises one or more mainframe computers, one or more work stations,
one or more personal computers, combinations thereof, and the like.

[0022]Information is transferred between the host computer 102 and
secondary storage devices managed by a data storage and retrieval system,
such as data storage and retrieval system 106, vial communication links
108, 110, and 112. Communication links 108, 110, and 112, comprise a
serial interconnection, such as an RS-232 cable or an RS-422 cable, an
Ethernet interconnection, a SCSI interconnection, a Fibre Channel
interconnection, an ESCON interconnection, a FICON interconnection, a
Local Area Network (LAN), a private Wide Area Network (WAN), a public
wide area network, Storage Area Network (SAN), Transmission Control
Protocol/Internet Protocol (TCP/IP), the Internet, combinations thereof,
and the like.

[0023]In the embodiment shown in FIG. 1, data storage and retrieval system
106 includes data storage devices 114 and 116. In alternative
embodiments, data storage and retrieval system 106 includes a single data
storage device. In alternative embodiments, data storage and retrieval
system 106 includes more than two data storage devices.

[0024]A plurality of portable tape storage media 118 are moveably disposed
within data storage and retrieval system 106. In certain embodiments, the
plurality of tape storage media 118 are housed in a plurality of portable
tape cartridges 120. Each such portable tape cartridges may be removeably
disposed in an appropriate data storage device.

[0025]Data storage and retrieval system 106 further includes program logic
to manage data storage devices 114 and 116, and plurality of portable
tape cartridges 120. In certain embodiments, each data storage devices
114 and 116 includes a controller, such as controllers 122 and 124,
comprising such program logic.

[0026]In alternative embodiments, data storage and retrieval system 106
and host computer 102 may be collocated on a single apparatus. In this
case, host computer 102 may be connected to another host computer to, for
example, translate one set of library commands or protocols to another
set of commands/protocols, or to convert library commands form one
communication interface to another, or for security, or for other
reasons.

[0027]Data storage and retrieval system 106 comprises a computer system,
and manages, for example, a plurality of tape drives and tape cartridges.
In such embodiments, data storage devices 114 and 116 may be any suitable
tape drives known in the art, e.g., the TotalStorage® 3590 tape drives
(TotalStorage is a trademark of IBM Corporation). Similarly, tape
cartridges 120 may be any suitable tape cartridge device known in the
art, such as ECCST, Magstar, TotalStorage® 3420, 3480, 3490E, 3580,
3590 tape cartridges, etc.

[0028]Referring now to FIG. 2, exemplary tape drive unit 200 is presented.
When writing to a magnetic tape storage medium, such as magnetic tape
202, a portion of the tape medium is disposed on a first rotatable reel,
such as reel 204, and a portion of the tape medium is disposed on a
second rotatable reel, such as reel 206. The rotatable reels are moved
such that tape storage medium 202 is move from one reel, past tape head
208, and onto the other reel. Tape head 208 comprises write head 210,
wherein write head 210 encodes information in tape storage medium 202 as
that medium travels past write head 210. As those skilled in the art will
appreciate, tape head 208 may comprise other elements and components not
shown in FIG. 2.

[0029]In the illustrated embodiment of FIG. 2, tape head 208 is in
communication with controller 214. In certain embodiments, controller 214
is integral with tape head 208. Further in the illustrated embodiment of
FIG. 2, controller 214 comprises processor 216 and data buffer 218.
Controller 214 is in communication with computer readable medium 220.
Instructions 222 are encoded in computer readable medium 220.

[0030]In certain embodiments, computer readable medium 220 is integral
with controller 214. In the illustrated embodiment of FIG. 2, reel 204,
reel 206, tape head 208, controller 214, and computer readable medium 220
are disposed within tape drive unit 200. As those skilled in the art will
appreciate, tape drive unit 200 may comprise other elements and
components not shown in FIG. 2.

[0032]FIG. 3A summarizes Applicants' method to evaluate the performance of
a data storage device. As those skilled in the art will appreciate, read
element 210 detects data encoded in a moving sequential information
storage medium 202. Read element 210 comprises one element in a read
channel which decodes data written to sequential information storage
medium 200. Such a read channel further comprises a finite impulse
response (FIR) filter, sometimes referred to as a mid-linear filter.

[0033]A FIR filter is a type of digital filter used in Digital Signal
Processing (DSP) applications. FIR filters are used to modify the
frequency response of ideal partial response maximum likelihood (PRML)
channels. As the frequency response of a recording channel changes over
time as a result of channel hardware usage, the FIR filter compensates
for nonlinear signal losses in an effort to maintain a match to an ideal
PRML channel frequency response. Further, a FIR tap is a
coefficient/delay pair indicative of the amount of memory required to
implement the filter, the number of calculations required, and the amount
of "filtering" the filter can do.

[0034]Applicants' method to evaluate the performance of a data storage
device utilizes a plurality of FIR taps. Referring now to FIG. 3A, in
step 305 the method provides a data storage device comprising a FIR
filter comprising (N) taps, wherein (N) is greater than or equal to 1. In
certain embodiments, (N) is greater than 1. In certain embodiments, (N)
is greater than 5.

[0035]In step 310, the method at a time t1 decodes a sequential
information storage medium using a read channel comprising, inter alia, a
FIR filter. In certain embodiments, step 310 is performed by a
controller, such as controller 214 (FIG. 2), disposed in the data storage
device of step 305. In certain embodiments, step 310 is performed by a
processor, such as processor 242 (FIG. 2), disposed in a host computer,
such as host computer 102 (FIG. 2), in communication with the data
storage device of step 305.

[0036]In certain embodiments initial time t1 is some time prior to the
sale of the tape drive unit and the (n) FIR taps are measured by the
manufacturer. In other embodiments, time t1 is some time subsequent to
the sale of the tape drive unit but prior to its use. In such an
embodiment, the (n) FIR taps are measured by the purchaser of the tape
drive unit. In yet other embodiments, time t1 occurs at any time during
the tape drive's life span.

[0037]In step 315, the method measures a (n)th FIR tap, wherein (n) is
initially set to 1. In certain embodiments, step 315 is performed by a
controller, such as controller 214 (FIG. 2), disposed in the data storage
device of step 305. In certain embodiments, step 315 is performed by a
processor, such as processor 242 (FIG. 2), disposed in a host computer,
such as host computer 102 (FIG. 2), in communication with the data
storage device of step 305.

[0038]In step 320, the method saves at least one time t1 (n)th FIR tap
value. In certain embodiments, the time t1 (n)th FIR tape value is
encoded in a computer readable medium, such as computer readable medium
220, disposed in the data storage device of step 305. In certain
embodiments, the time t1 (n)th FIR tape value is encoded in a computer
readable medium, such as computer readable medium 244, disposed in a host
computer in communication with the data storage device of step 305. In
certain embodiments, step 320 is performed by a controller, such as
controller 214 (FIG. 2), disposed in the data storage device of step 305.
In certain embodiments, step 320 is performed by a processor, such as
processor 242 (FIG. 2), disposed in a host computer, such as host
computer 102 (FIG. 2), in communication with the data storage device of
step 305.

[0039]In step 325, the method determines if all (N) FIR taps have been
monitored, i.e. if (n) equals (N). In certain embodiments, step 325 is
performed by a controller, such as controller 214 (FIG. 2), disposed in
the data storage device of step 305. In certain embodiments, step 325 is
performed by a processor, such as processor 242 (FIG. 2), disposed in a
host computer, such as host computer 102 (FIG. 2), in communication with
the data storage device of step 305.

[0040]If the method determines in step 325 that all (N) FIR taps have not
been monitored, then the method transitions from step 325 to step 330
wherein the method increments (n). The method transitions from step 330
to step 315 and continues as described herein.

[0041]Alternatively, if the method determines in step 325 that all (N) FIR
taps have been monitored, then the method transitions from step 325 to
step 335 wherein the method at a time t2, wherein time t2 is later than,
i.e. subsequent to, time t1, decodes a sequential information storage
medium using a read channel comprising, inter alia, a FIR filter. In
certain embodiments, the sequential information storage medium of step
335 is the same sequential information storage medium that was used in
step 310. In certain embodiments, the sequential information storage
medium of step 335 differs from the sequential information storage medium
that was used in step 310.

[0042]In certain embodiments, step 335 is performed by a controller, such
as controller 214 (FIG. 2), disposed in the data storage device of step
305. In certain embodiments, step 335 is performed by a processor, such
as processor 242 (FIG. 2), disposed in a host computer, such as host
computer 102 (FIG. 2), in communication with the data storage device of
step 305.

[0043]In step 340, the method measures a (j)th FIR tap, wherein (j) is
initially set to 1. In certain embodiments, a (n)th FIR tap of step 315
corresponds to a (j)th FIR tap of step 340. In certain embodiments, step
340 is performed by a controller, such as controller 214 (FIG. 2),
disposed in the data storage device of step 305. In certain embodiments,
step 340 is performed by a processor, such as processor 242 (FIG. 2),
disposed in a host computer, such as host computer 102 (FIG. 2), in
communication with the data storage device of step 305.

[0044]In step 345, the method saves at least one time t2 (j)th FIR tap
value. In certain embodiments, the time t2 (j)th FIR tape value is
encoded in a computer readable medium, such as computer readable medium
220, disposed in the data storage device of step 305. In certain
embodiments, the time t2 (j)th FIR tape value is encoded in a computer
readable medium, such as computer readable medium 244, disposed in a host
computer in communication with the data storage device of step 305. In
certain embodiments, step 345 is performed by a controller, such as
controller 214 (FIG. 2), disposed in the data storage device of step 305.
In certain embodiments, step 345 is performed by a processor, such as
processor 242 (FIG. 2), disposed in a host computer, such as host
computer 102 (FIG. 2), in communication with the data storage device of
step 305.

[0045]In step 350, the method determines if all (N) FIR taps have been
monitored at time t2, i.e. if (j) equals (N). In certain embodiments,
step 350 is performed by a controller, such as controller 214 (FIG. 2),
disposed in the data storage device of step 305. In certain embodiments,
step 350 is performed by a processor, such as processor 242 (FIG. 2),
disposed in a host computer, such as host computer 102 (FIG. 2), in
communication with the data storage device of step 305.

[0046]If the method determines in step 350 that all (N) FIR taps have not
been monitored at time t2, then the method transitions from step 350 to
step 355 wherein the method increments (n). The method transitions from
step 355 to step 340 and continues as described herein.

[0047]FIG. 4 graphically illustrates two sets of FIR tap values. The
second set of FIR tap values were measured at t2, and therefore, were
taken subsequent to the first set and after some amount of usage of the
data storage device of step 305.

[0048]If the method determines in step 350 that all (N) FIR taps have been
monitored at time t2, then the method transitions from step 350 to step
360 wherein the method forms a transfer functions (n) by computing a
Fourier Transform of the (N) FIR tap values obtained at time t1. In
certain embodiments, step 360 is performed by a controller, such as
controller 214 (FIG. 2), disposed in the data storage device of step 305.
In certain embodiments, step 360 is performed by a processor, such as
processor 242 (FIG. 2), disposed in a host computer, such as host
computer 102 (FIG. 2), in communication with the data storage device of
step 305.

[0049]In step 365, the method forms a transfer function (j) by computing a
Fourier Transform of the (N) FIR tap values obtained at time t2. In
certain embodiments, step 365 is performed by a controller, such as
controller 214 (FIG. 2), disposed in the data storage device of step 305.
In certain embodiments, step 365 is performed by a processor, such as
processor 242 (FIG. 2), disposed in a host computer, such as host
computer 102 (FIG. 2), in communication with the data storage device of
step 305.

[0050]The Fourier Transform of (N) FIR taps calculates a read equalizer
transfer function, or a magnitude of signal attenuation, as a function of
magnetic flux reversal spatial density, as illustrated in FIG. 5, where
the transfer function magnitude is normalized to unity at its maximum
value.

[0051]In step 370, the method forms a FIR magnitude response ratio curve
by dividing the (j) FIR transfer function of step 365 by the (n) FIR
transfer function of step 360. In certain embodiments, step 370 is
performed by a controller, such as controller 214 (FIG. 2), disposed in
the data storage device of step 305. In certain embodiments, step 370 is
performed by a processor, such as processor 242 (FIG. 2), disposed in a
host computer, such as host computer 102 (FIG. 2), in communication with
the data storage device of step 305.

wherein d is the total effective loss parameter (in spatial units), which
includes any physical head-media separation from recording and/or read
back operations and any changes in flux transition width, and L is the
magnetic transition density (in flux reversals per spatial unit).

[0053]Referring now to FIG. 3c, in step 375 the method establishes a
Wallace spacing loss parameter. In certain embodiments, step 375 is
performed by the manufacturer of the data storage device of step 305. In
certain embodiments, step 375 is performed by the manufacturer of a data
storage library, such as data storage library 106 which includes the data
storage device of step 305. In certain embodiments, step 375 is performed
by the owner of the data storage device of step 305. In certain
embodiments, step 375 is performed by the operator of the data storage
device of step 305.

[0054]In step 380 the method determines an actual Wallace spacing loss
parameter at time t2 by performing a least mean squared (LMS) fit of the
FIR magnitude response ratio curve of step 370. Applicants' LMS method is
a method of fitting data where the best fit is that instance of the model
for which the sum of squared residuals has its least value (a residual
being the difference between an observed value and the value given by the
model). Using LMS method the total effective loss parameter d can be
readily computed by solving the following two partial differential
equations for d:

[0055]FIG. 6 illustrates the FIR magnitude response ratio curve between
time t2 and t1 and the LMS fit of the Wallace spacing loss parameter to
this ratio curve. For the given example, the change in effective magnetic
spacing is 35 nanometers.

[0056]In step 385, the method determines if the actual Wallace spacing
loss parameter for time t2 of step 380 is greater than the Wallace
spacing loss parameter threshold of step 375. In certain embodiments,
step 385 is performed by a controller, such as controller 214 (FIG. 2),
disposed in the data storage device of step 305. In certain embodiments,
step 385 is performed by a processor, such as processor 242 (FIG. 2),
disposed in a host computer, such as host computer 102 (FIG. 2), in
communication with the data storage device of step 305.

[0057]If the method determines in step 385 that the actual Wallace spacing
loss parameter for time t2 of step 380 is greater than the Wallace
spacing loss parameter threshold of step 375, then the method transitions
from step 385 to step 390 wherein the data storage device of step 305 is
taken out of service. In certain embodiments, step 390 comprises
generating a message to take said data storage device out of service.

[0058]Alternatively, if the method determines in step 385 that the actual
Wallace spacing loss parameter for time t2 of step 3 80 is not greater
than the Wallace spacing loss parameter threshold of step 375, then the
method transitions from step 385 to step 395 wherein the method, using
the actual time t2 Wallace spacing loss parameter of step 380, and using
any prior actual Wallace spacing loss parameter(s), predicts a future
time t3, wherein time t3 is subsequent to time t2, when an actual Wallace
spacing loss parameter for the data storage device of step 305 is likely
to be greater than the Wallace spacing loss parameter threshold of step
375.

[0059]In certain embodiments, step 395 is performed by a controller, such
as controller 214 (FIG. 2), disposed in the data storage device of step
305. In certain embodiments, step 395 is performed by a processor, such
as processor 242 (FIG. 2), disposed in a host computer, such as host
computer 102 (FIG. 2), in communication with the data storage device of
step 305.

[0060]In step 399, the method schedules for future time t3 a follow-up
evaluation of the data storage device of step 305 using Applicants'
method described herein. In certain embodiments, step 399 is performed by
a controller, such as controller 214 (FIG. 2), disposed in the data
storage device of step 305. In certain embodiments, step 399 is performed
by a processor, such as processor 242 (FIG. 2), disposed in a host
computer, such as host computer 102 (FIG. 2), in communication with the
data storage device of step 305.

[0061]As will be understood, by an individual or ordinary skill in the
art, Applicants' method described herein can be performed without having
physical access to the device. For example, host computer 102 (FIGS. 1,
2) may be external to data storage devices 122 and/or 124. Nevertheless,
data storage devices 122 and/or 124 can be evaluated using Applicants'
method using the program readable program code 426 encoded in computer
readable medium 244 disposed in host computer 102.

[0062]In certain embodiments, an actual Wallace spacing loss parameter d
can be used to determine whether a tape drive unit should be replaced or
maintenance before a failure occurs. In such embodiments, an actual
Wallace spacing loss parameter may be determined at regular intervals and
checked against the threshold of step 375 (FIG. 3c). When an actual
Wallace spacing loss parameter exceeds the threshold, then corrective
action can be taken to maintain the integrity of the data storage system.
Thus, an actual Wallace spacing loss parameter can be used to assess
changes to magnetic recording system components (e.g. head transducer or
media) and is a useful method of evaluating component usage effects (e.g.
wear, recession, material build-up, debris accumulation, ESD, corrosion,
self-acting air bearing thickness, etc).

[0063]In certain embodiments, individual steps recited in FIGS. 3, 3B,
and/or 3C, may be combined, eliminated, or reordered. In other
embodiments, computer readable program code, such as computer readable
program code 222 (FIG. 2) and/or computer readable program code 246 (FIG.
2), encoded in a computer readable medium, such as computer readable
medium 220 (FIG. 2) and/or 244 (FIG. 2), is executed by a processor, such
as processor 214 (FIG. 2) and/or processor 242 (FIG. 2), to perform one
or more of steps recited in FIGS. 3A, 3B, and/or 3C. In yet other
embodiments, the invention includes computer readable program code
resident in any other computer program product encoded in a computer
readable medium, where that computer readable program code is executed by
a computer external to, or internal to, a data storage system, to perform
one or more of steps recited in FIGS. 3A, 3B, and/or 3C In either case,
the computer readable program code may be encoded in computer readable
medium comprising, for example, a magnetic information storage medium, an
optical information storage medium, an electronic information storage
medium, and the like. "Electronic storage media," may mean, for example
and without limitation, one or more devices, such as and without
limitation, a PROM, EPROM, EEPROM, Flash PROM, compactflash, smartmedia,
and the like.

[0064]While the preferred embodiments of the present invention have been
illustrated in detail, it should be apparent that modifications and
adaptations to those embodiments may occur to one skilled in the art
without departing from the scope of the present invention as set forth in
the following claims.

Patent applications by Eric Rolf Christensen, Tucson, AZ US

Patent applications by International Business Machines Corporation

Patent applications in class MONITORING OR TESTING THE PROGRESS OF RECORDING

Patent applications in all subclasses MONITORING OR TESTING THE PROGRESS OF RECORDING